Many machines for assembling and disassembling tired wheels have been proposed up to now. Thus, for example, the European patent application EP-1 177 920 teaches a machine for assembling and disassembling a tire onto and from a wheel rim, that comprises a base on which a wheel bearing table is mounted for rotation and from which a column extends upwards at the rear side of the base.
Parallel straight guides are provided on the column that are substantially vertical, in use, and on which a device for assembling and disassembling a tire onto and from a wheel rim is slidably mounted. Such a device comprises a carriage that is slidably mounted along the guides and bears a sleeve having a substantially horizontal axis which supports one end of a hollow shaft that overhangingly extends from the sleeve. The hollow shaft at its end secured to the sleeve abuts against one end of the cylinder of a cylinder-and-piston jack, whereas at its other end or distal end it supports a hollow head having an inner opening larger in size than that of the hollow shaft.
The piston rod of the jack extends throughout the entire or almost the entire length of the hollow shaft, and by means of a leverage it controls a disassembling tool supported by the hollow head and protruding therefrom. More particularly, the disassembling tool is pivoted in order to be angularly displaceable about an articulation axis at right angles with the axis of the hollow shaft.
By controlling the forward/back movements of the jack piston rod, one controls the angular movements of the disassembling tool at the front of the hollow shaft.
At the diametrically opposite position with respect to the disassembling tool, an auxiliary assembling tool is secured to the hollow head.
In order to disassemble a tire from its wheel rim once the latter has been blocked on the wheel rim bearing table, one proceeds first to bead break the tire, as is common practice in the art, by using a suitable bead breaking tool, then the carriage is caused to slide along the guides to bring the tool tip immediately above the tire bead close to the edge of the wheel rim. At this point, a further movement of the carriage occurs along the guides to cause the hollow shaft to approach to the wheel rim, and then upon energizing the jack the disassembling tool is arranged in a tire bead “grasping” position, in which the tool tip is directed according to the axis of rotation of the wheel bearing table. The hollow shaft then continues or is forced to lower so as to cause the tool to enter between tire and wheel rim until the hook tip of the tool has engaged, i. e. grasped, from the inside the bead of the tire. At that point, the operator controls a backward movement of the jack piston rod, so as to tilt, while being angularly displaced, the tool up to bring it in a position indicated as “extraction” position of the bead.
Such a machine is rather complex to manufacture and also requires the execution of tool control operations in any operating steps. The device is defined as being automatic, although as a matter of fact it is permanently controlled by the operator.
The European patent application EP-1 398 184 also discloses a device similar to that described above, which is controlled and guided throughout all the disassembling steps through controls given by suitable actuators.
The European patent application EP-1 714 807 in the name of the applicant of the present patent application discloses a tire assembling-disassembling machine comprising a base, a wheel bearing table supported by the base, by a column rising from the base and a tool bearing arm that overhangingly extends from the column on which it is slidably mounted. The tool bearing arm extends in a radial direction with respect to a wheel rim mounted on the wheel bearing table, and can be caused to move in a direction substantially parallel to the axis of rotation of the wheel rim on the wheel bearing table.
At its overhanging end, the tool bearing arm supports, either directly or through a link element, a bill element that constitutes the actual tool.
Between bill element and tool bearing arm, elastic loading means (e. g. a spring) can be provided which are designed to keep the bill element in a substantially vertical trim.
In order to dismount a tire by means of such a bill tool, a tired wheel is arranged and blocked on the wheel bearing table of the machine. One proceeds to bead breaking the tire and then, by suitably lowering the tool bearing arm, the bill tip is brought to abut against the wheel rim edge close to the tire bead. The tool bearing arm is then further lowered, thereby forcing the bill tip to enter between tire bead and edge of the wheel rim until the bead is engaged from the inside at an inner recess of the bill.
The bill is then progressively raised in a substantially vertical trim and is forced to angularly move backwards, thereby automatically taking an inclined trim with respect to a vertical line. The bill brings with it the hooked bead to move it outside the edge of the wheel rim. At that point, it will be sufficient to cause the wheel rim or the tool to rotate in order to move the entire tire bead beyond the edge of the wheel rim.
Such a solution is surely simpler than the two previous ones, and is quite satisfactory for cars, whereas it is not always suitable for large size wheels, such as lorry wheels.
WO-2009-13 83 22, WO-2009 13 01 35, EP-2 463 125 disclose respective prior art tools for disassembling a tire from a wheel rim.